Main Session
Sep 29
PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care

3510 - Beyond Daily IGRT: Offline Adaptive Tomotherapy with Daily MVCT In 233 Patients with Head and Neck Cancer: A Prospective Registry of Adaptation Rates, Failure Patterns, and Survival

03:45pm - 05:00pm ET
Poster Hall - Exhibit Hall A
Screen: 10
POSTER

Presenter(s)

Sarath K V, MD, MBBS - Amrita Institute of Medical Sciences and Research Centre, Faridabad, -1

S. K V1, R. Kumar2, B. Vishwanathan2, U. Gupta1, R. Kamal2, D. Manigandan3, D. Thaper2, R. R. Shinde4, C. Choudhary4, and U. K. Maheshwari4; 1Amrita Institute of Medical Sciences and Research Centre, Amrita Vishwa Vidyapeetham, Faridabad, -1, India, 2Amrita Institute of Medical Sciences and Research Centre, Faridabad, India, 3Amrita Institute of medical science, FARIDABAD, India, 4Amrita Institute of medical science, Faridabad, India

Purpose/Objective(s):

Anatomic changes during radiotherapy for head and neck squamous cell carcinoma (HNSCC) can compromise target coverage and increase normal tissue dose. Although offline adaptive radiotherapy (ART) can correct these deviations, prospective data defining adaptation frequency, workflow feasibility, and clinical implications remain limited, particularly with helical Tomotherapy. We report a prospective single institution registry evaluating the necessity, efficiency, patterns of failure and outcomes of a structured offline adaptive workflow using daily MVCT

Materials/Methods:

This ethics approved registry enrolled 233 consecutive HNSCC patients treated with helical Tomotherapy (March 2023–Feb 2026): adjuvant (n=146; 60–66 Gy) or definitive (n=87; 66–70 Gy). 68% in definitive cases and 12% in Adjuvant cases received concurrent chemotherapy. Daily MVCT was acquired for every fraction with deformable dose accumulation (PreciseART). Replanning was triggered if two consecutive scans showed CTV D95% <98%, PTV D95% <95%, hotspot >105% (2 cc), or OAR violation. Endpoints included adaptation metrics, overall treatment time (OTT), recurrence patterns with field analysis and survival. Median follow up was 14 months

Results:

Despite daily IGRT, 100% patients required =1 adaptive replan; 34% required =2 and 5% =3. Median fraction at first replan was 17. Adaptive workflow was efficient (median 20 minutes) and did not prolong therapy (median OTT 43 days); 100% of adjuvant patients completed RT within 12 weeks post surgery (median package time 77 days).

In the adjuvant cohort, 31/146 (21%) recurred at a median of 3.58 months. Isolated local failure occurred in 23%, in field only recurrence occurred in 26%; whereas 71% of failures contained a distant component; distant only metastasis occurred in 38%, no mortality during RT

In the definitive cohort (n=87), majorly had oropharynx primary, Complete Response was achieved in 57%, Stable/residual disease in 11 (13%), 26% developing progression and 12 deaths (1 during RT)

Across both cohorts, total disease events were 27% and were followed up for a median of 14 months

Conclusion:

Universal adaptive replanning was required despite daily IGRT, indicating image guidance alone does not fully mitigate clinically significant dosimetric deviations. Structured offline adaptation was feasible without treatment delay. Among post operative recurrences, the predominance of distant over isolated local failure, coupled with early recurrence kinetics, identifies systemic progression as the principal residual challenge. These findings support routine integration of adaptive workflows and suggest that structured early (~3-month) post treatment surveillance imaging merits consideration

Keywords: Adaptive radiotherapy; HNSCC; Patterns of failure